A method and apparatus for determining embedded runout correction values uses a closed-loop system (with feedback) in a disk drive. Optionally, the embedded runout correction values may be determined after the disk drive has been manufactured and placed in the field. In addition, the embedded runout correction values may be updated after the disk drive has been manufactured and placed in the field.
|
1. A method of determining embedded runout correction (erc) values in a disk drive, wherein the disk drive includes a transducer, a disk and a servo control system, the transducer reads data from and writes data to the disk, the disk includes tracks, the tracks each include servo sectors, the erc values provide compensation for repeatable runout (RRO) in the tracks, and a position error signal (pes) positions the transducer relative to the tracks, the method comprising:
determining a first erc value using the transducer to read a servo sector during a first revolution of the disk;
determining a second erc value using the first erc value and the transducer to read the servo sector during a second revolution of the disk;
determining an updated erc value for the servo sector using the first and second erc values;
writing the updated erc value to the servo sector;
generating a third pes using the transducer to read the updated erc value and servo bursts in the servo sector during a third revolution of the disk; and
using the third pes to position the transducer as the transducer writes user data to a data field that is adjacent to the servo sector during the third revolution of the disk.
11. A method of determining embedded runout correction (erc) values in a disk drive, wherein the disk drive includes a transducer, a disk and a servo control system, the transducer reads data from and writes data to the disk, the disk includes tracks, the tracks each include servo sectors, the erc values provide compensation for repeatable runout (RRO) in the tracks, and a position error signal (pes) positions the transducer relative to the tracks, the method comprising:
generating a first pes using the transducer to read a servo sector during a first revolution of the disk;
determining a first erc value for the servo sector using the first pes;
generating a second pes using the first erc value and the transducer to read the servo sector during a second revolution of the disk;
determining a second erc value for the servo sector using the second pes;
determining an updated erc value for the servo sector using the first and second erc values;
writing the updated erc value to the servo sector;
generating a third pes using the transducer to read the updated erc value and servo bursts in the servo sector during a third revolution of the disk; and
using the third pes to position the transducer as the transducer writes user data to a data field that is adjacent to the servo sector during the third revolution of the disk.
31. A method of determining embedded runout correction (erc) values in a disk drive, wherein the disk drive includes a transducer, a disk and a servo control system, the transducer reads data from and writes data to the disk, the disk includes tracks, the tracks each include servo sectors, the erc values provide compensation for repeatable runout (RRO) in the tracks, and a position error signal (pes) positions the transducer relative to the tracks, the method comprising:
generating a first pes using the transducer to read a servo sector during a first revolution of the disk;
determining a first erc value for the servo sector by applying the first pes to an inverse transfer function of the servo control system;
calculating a calculated pes by applying the first erc value to a transfer function of the servo control system;
generating a second pes using the calculated pes, the first erc value and the transducer to read the servo sector during a second revolution of the disk;
determining a second erc value for the servo sector by applying the second pes to the inverse transfer function of the servo control system;
determining an updated erc value for the servo sector using the first and second erc values;
writing the updated erc value to the servo sector;
generating a third pes using the transducer to read the updated erc value and servo bursts in the servo sector during a third revolution of the disk; and
using the third pes to position the transducer as the transducer writes user data to a data field that is adjacent to the servo sector during the third revolution of the disk.
41. A method of determining embedded runout correction (erc) values in a disk drive after the disk drive has been manufactured and is in the possession of an end user and is operably connected to a host computer, wherein the disk drive includes a transducer, a disk and a servo control system, the transducer reads data from and writes data to the disk, the disk includes tracks, the tracks each include servo sectors, the erc values provide compensation for repeatable runout (RRO) in the tracks, and a position error signal (pes) positions the transducer relative to the tracks, the method comprising:
generating a first pes using the transducer to read a servo sector during a first revolution of the disk;
determining a first erc value for the servo sector by applying the first pes to an inverse transfer function of the servo control system;
calculating a calculated pes by applying the first erc value to a transfer function of the servo control system;
generating a second pes using the calculated pes, the first erc value and the transducer to read the servo sector during a second revolution of the disk;
determining a second erc value for the servo sector by applying the second pes to the inverse transfer function of the servo control system;
determining an updated erc value for the servo sector using the first and second erc values;
writing the updated erc value to the servo sector;
generating a third pes using the transducer to read the updated erc value and servo bursts in the servo sector during a third revolution of the disk; and
using the third pes to position the transducer as the transducer writes user data to a data field that is adjacent to the servo sector during the third revolution of the disk.
2. The method of
3. The method of
5. The method of
6. The method of
7. The method of
8. The method of
9. The method of
10. The method of
12. The method of
13. The method of
14. The method of
15. The method of
16. The method of
17. The method of
18. The method of
19. The method of
20. The method of
generating a prior pes using the transducer to read the servo sector during a prior revolution of the disk;
determining a prior erc value for the servo sector using the prior pes;
generating the first pes using the prior erc value and the transducer to read the servo sector during the first revolution of the disk; and
determining the updated erc value using the prior, first and second erc values.
21. The method of
generating a later pes using the first and second erc values and the transducer to read the servo sector during a later revolution of the disk between the second and third revolutions of the disk;
determining a third erc value for the servo sector using the later pes; and
determining the updated erc value using the first, second and third erc values.
22. The method of
calculating a calculated pes using the first erc value; and
determining the second pes using the calculated pes, the first erc value and the transducer to read the servo sector during the second revolution of the disk.
23. The method of
24. The method of
25. The method of
26. The method of
27. The method of
28. The method of
29. The method of
30. The method of
32. The method of
33. The method of
34. The method of
35. The method of
36. The method of
37. The method of
calculating a second calculated pes by applying the second erc value to the transfer function of the servo control system;
generating a later pes using the second calculated pes, the first and second erc values and the transducer to read the servo sector during a later revolution of the disk between the second and third revolutions of the disk;
determining a third erc value for the servo sector by applying the later pes to the inverse transfer function of the servo control system; and
determining the updated erc value using the first, second and third erc values.
38. The method of
39. The method of
40. The method of
42. The method of
43. The method of
44. The method of
45. The method of
46. The method of
47. The method of
calculating a second calculated pes by applying the second erc value to the transfer function of the servo control system;
generating a later pes using the second calculated pes, the first and second erc values and the transducer to read the servo sector during a later revolution of the disk between the second and third revolutions of the disk;
determining a third erc value for the servo sector by applying the later pes to the inverse transfer function of the servo control system; and
determining the updated erc value using the first, second and third erc values.
48. The method of
49. The method of
50. The method of
51. The method of
52. The method of
53. The method of
54. The method of
55. The method of
56. The method of
57. The method of
58. The method of
reading the user data from the data field;
storing the user data in a buffer; and then
writing the updated erc value to the servo sector and the user data to the data field during a single revolution of the disk.
59. The method of
60. The method of
|
This application claims priority from U.S. Provisional Patent Application Ser. No. 60/339,463 filed Dec. 11, 2001, which is incorporated herein by reference in its entirety.
The present invention relates to transducer positioning in a magnetic data storage system, such as a computer disk drive. More particularly, the present invention relates to a method and apparatus for compensating for repeatable run-out (RRO) in a magnetic data storage system.
A disk drive is a data storage device that stores digital data in tracks on the surface of a data storage disk. Data is read from or written to a track of the disk using a transducer, which includes a read element and a write element, that is held close to the track while the disk spins about its center at a substantially constant angular velocity. To properly locate the transducer near the desired track during a read or write operation, a closed-loop servo system is generally implemented. The servo system uses servo data read from the disk surface to align the transducer with the desired track. The servo data is generally written to the disk using a servo track writer (STW). However, there has been a movement towards having the disk drive self-servo write some portion or, in some cases, all of the servo data.
In an ideal disk drive, the tracks of the disk are non-perturbed circles situated about the center of the disk. As such, each of these ideal tracks includes a track centerline that is located at a known constant radius from the disk center. In an actual system, however, it is difficult to write non-perturbed circular tracks to the disk. That is, due to certain problems (e.g., vibration, bearing defects, inaccuracies in the STW and disk clamp slippage), tracks are generally written differently from the ideal non-perturbed circular track shape. Positioning errors created by the perturbed nature of these tracks are known as written-in repeatable runout (WRRO).
The perturbed shape of these tracks complicates the transducer positioning function during read and write operations because the servo system needs to continuously reposition the transducer during track following to keep up with the constantly changing radius of the track centerline with respect to the center of the spinning disk. Furthermore, the perturbed shape of these tracks can result in problems such as track squeeze and track misregistration errors during read and write operations.
In order to reduce such problems, disk drive manufacturers have developed techniques to measure the WRRO so that compensation values (also known as embedded runout correction values or ERC values) may be generated and used to position the transducer along an ideal track centerline. Examples of such techniques may be found in U.S. Pat. No. 4,412,165 to Case et al. entitled “Sampled Servo Position Control System,” U.S. Pat. No. 6,115,203 to Ho et al. entitled “Efficient Drive-Level Estimation of Written-In Servo Position Error,” and U.S. Pat. No. 6,549,362 to Melrose et al. entitled “Method and Apparatus for the Enhancement of Embedded Runout Correction in a Disk Drive,” all of which are incorporated herein by reference.
In general, correcting poorly-written tracks takes place in a self-test procedure at the factory (i.e., during the manufacturing process); that is, before the disk drive is delivered to an end user. Each disk drive is required to complete its self-test procedure within a predetermined period of time. If a disk drive does not complete its self-test procedure within the predetermined period of time, it fails the self-test procedure and is discarded.
As is understood by those skilled in the art, the process of determining ERC values during the manufacturing process is somewhat time consuming. While it would be beneficial to develop ERC values for each and every sector of each and every track of a disk drive during the manufacturing process, this is rarely done because the disk drive would likely fail its self-test procedure. Furthermore, manufacturing times would become excessive if ERC values were developed in such a manner.
Accordingly, disk drive manufacturers have developed techniques that are used in the manufacturing process, which attempt to correct only the most poorly-written tracks of a disk drive, instead of all of the tracks of each disk drive. In such techniques, an ERC threshold is used in determining which tracks are to be corrected.
More specifically, in one technique, a position error signal (PES) due to repeatable runout (PES RRO) is measured by track following and averaging the position error from the servo bursts in each servo sector associated with the track for multiple revolutions (e.g., 25 revolutions) of the disk. As will be understood by those skilled in the art, the position error is averaged for multiple revolutions of the disk in an attempt to average-out the affects of non-repeatable runout (NRRO).
If the absolute value of the average PES RRO for any servo sector in the track exceeds the ERC threshold, the track is corrected. That is, ERC values are determined for all of the servo sectors of that track. However, if the absolute value of the average PES RRO for each of the servo sectors in the track is less than the ERC threshold, the track is not corrected.
U.S. patent application Ser. No. 10/029,528 filed Dec. 20, 2001 describes a method and apparatus for automatically determining ERC thresholds on a drive-by-drive basis in order to make efficient use of the self-test time available to correct tracks. Such application is incorporated herein by reference in its entirety.
Since attempts are made to correct only the most poorly written tracks in a disk drive, many other poorly written tracks may still be included in a disk drive when it reaches an end user. Furthermore, a disk drive's parameters (e.g., flying height, head linearity, magnetic image, burst sizes, etc.) may change, which may require adjustment of the ERC values after a disk drive has left the factory and is in the possession of an end user. Accordingly, it would be desirable to correct the tracks after the disk drive has left the factory and been provided to an end user.
Prior techniques for correcting poorly-written tracks by generating ERC values have been open-loop techniques. One example of a prior open-loop technique is illustrated in
With reference to
In step 20, the inverse impulse response for the disk drive is obtained. As will be understood by those skilled in the art, the inverse impulse response may be obtained in a variety of ways, including those described in U.S. Pat. Nos. 6,115,203 and 6,549,362. Furthermore, the inverse impulse response may be obtained for each transducer in a disk drive as described in U.S. Pat. No. 6,549,362.
Next, in step 25, the average PES RRO is circularly convolved with the inverse impulse response to obtain the WRRO. Finally, in step 30, the ERC values are determined and written to the disk surface based upon the WRRO.
While the technique of
Accordingly, it would be desirable to provide a method and apparatus for determining ERC values that overcomes the deficiencies of open-loop systems.
The present invention is designed to meet the aforementioned, and other, needs. The invention is directed to method and apparatus for determining ERC values using a closed-loop system (i.e., with feedback).
In one embodiment, the present invention provides a disk surface having a track written thereon. ERC values are determined for the track using feedback.
In another embodiment, the ERC values are determined after the disk drive has completed its in-factory manufacturing and been placed in the field.
In another embodiment, the ERC values are updated after the disk drive has completed its in-factory manufacturing and been placed in the field.
Other embodiments, objects, features and advantages of the invention will be apparent from the following specification taken in conjunction with the following drawings.
While this invention is susceptible of embodiments in many different forms, there are shown in the drawings and will herein be described in detail, preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiments illustrated.
As illustrated in
Although the disk 108 illustrated in
The disk drive 100 includes a servo control system 144 for controlling the position of the transducer 124 with respect to the track 132 being followed. In general, the servo control system 144 comprises the transducer 124 being positioned, which reads position error information from the servo sectors 212, the actuator arm assembly 116 from which the transducer 124 is suspended, the voice coil motor 128, the controller 136 and the channel 140. As will be described in greater detail below, the response of the servo control system 144 to a given input is given by the impulse response of the servo control system 144.
Track 132 is ideally non-perturbed and ideally shares a common center 200 with the disk 108, such as the ideal track 216 illustrated in
A perturbed or non-ideal track 132 is difficult for the transducer 124 to follow because the position of the transducer 124 must constantly be adjusted by the servo control system 144. Consequently, the positioning of the transducer 124 is not as accurate on the written track 132 as it would be on the ideal track 216. As will be described in greater detail below, the present invention provides a method and apparatus for determining ERC values using feedback. By using ERC values determined using feedback (i.e., a closed-loop technique), the transducer 124 may more closely follow the path of an ideal track (such as track 216) using the servo information written in a non-ideal track (such as track 132), as compared to ERC values determined using open-loop techniques. Accordingly, the present invention may be used to approximate a disk drive having a disk with tracks that are almost perfectly-written.
As mentioned above, the tracks 132 on the disk 108 are each divided into data fields 208 and servo sectors 212. The servo sectors 212 include, among other things, information for use by the disk drive 100 in locating the transducer 124 above a desired track 132. When a host computer requests that data be read from or written to a particular data field 208 in a particular track 132, the transducer 124 must be moved to the track 132 and then must be positioned at a predetermined location relative to the centerline of the track 132 before a data transfer can take place. For purposes of illustrating the present invention, it will be assumed that the transducer 124 should be placed on the track centerline in order to read from and write to the disk 108. It should be understood that the invention is not limited to solely reading and writing when the transducer 124 is placed at the track centerline. As noted above, the present invention allows the transducer 124 to follow the ideal representation (ideal track 216) of a track 132 that is perturbed as written to the disk 108.
The disk drive 100 uses the information stored in the servo sectors 212 to first locate the desired track 132 and to then appropriately position the transducer 124 with respect to the centerline of the desired track 132. The data fields 208 include user data that can be accessed by a host computer. In general, the number of servo sectors 212 per track 132 on the disk 108 is a matter of design choice. The number may be dictated by, for example, a servo update rate.
To center the transducer 124 using the A and B bursts, the transducer 124 is first moved to the desired track 132 during a seek operation and, once there, reads the A and B bursts on the desired track 132. The signal magnitudes resulting from reading the A and B bursts are then combined (such as by subtracting the B burst magnitude from the A burst magnitude) to achieve the PES. The PES indicates the distance between the center of the transducer head 124 and the centerline (e.g., centerline 320b) of the desired track 132. The PES is used by the disk drive 100 to change the position of the transducer 124 to one that is closer to the desired (centered) position. This centering process is repeated for each successive servo sector 212 on the track 132 until the requested read/write operation has been performed in the appropriate data field 208. It should be appreciated that the present invention may be used with other schemes for storing servo information on a disk, such as schemes having four or more servo bursts, or, schemes that use zones, constant linear density (CLD) recording, split data fields, and/or hybrid servo.
Traditionally, the A bursts 304, 312 and the B bursts 308, 316 as well as all other servo information have been written to the disk surface 204 using a STW after the disk 108 is assembled into the disk drive 100 during the manufacturing processes. However, a variety of methods have now been developed which do not only use the STW for writing servo information onto the disk surface 204. For example, techniques have been developed which allow a portion of the servo information to be written through use of a STW and another portion of the servo information to be self-written by the transducers 124. Furthermore, in another technique, the transducers 124 may self-write the entirety of the servo information. In a further technique, printed media may be used by the transducers 124 to self-write some or all of the servo information. It should be understood that the present invention may be used regardless of the manner by which servo information is written onto the disk surface 204. For example, WRRO may occur even though only some (or in some cases none) of the WRRO is due to a STW. That is, the servo information does not necessarily have to be written using a STW.
The A and B bursts define the locations of the tracks 132 on the disk 108. That is, on a non-ideal track (such as track 132), the A and B bursts are written such that the centerline of the track 132 does not describe a perfect circle, but rather is perturbed. However, the transducer 124 can follow the path of an ideal track 216 by an adding an appropriate ERC or offset value in the servo sectors 212 of a particular track 132. As illustrated in
If the transducer 124 is to follow a perturbed path, such as that of a non-ideal track 132, the position of the transducer 124 must constantly be adjusted as the disk 108 rotates. Therefore, when performing conventional track following on a non-ideal track 132, adjustments are constantly made to position the transducer 124 to keep it centered on the track 132. The transducer 124 position is adjusted, as described above, by deriving a PES from the servo bursts, such the A burst 312 and the B burst 308 where the centerline 320b is followed. The PES creates a control signal for the voice coil motor 128 (or other movement means) to move the transducer 124 an appropriate amount. Because the transducer 124 position is continuously being adjusted, perfect or near perfect registration between the transducer 124 and the centerline of the track 132 (e.g., centerline 320b) is rarely achieved. This can create problems such as high track misregistration values.
As illustrated in
As illustrated in
As mentioned above, prior techniques for determining the ERC values are open-loop systems. In one such system (described in connection with
In contrast, in a preferred embodiment of the present invention, the ERC values are updated continuously (rather than in a batch process). Importantly, when determining the ERC value for a given servo sector 212, the present invention utilizes the position error (which includes both PES RRO and NRRO) introduced during the previous revolution of the disk 108. Accordingly, the ERC values are determined using feedback.
When determining the ERC values, certain initial conditions must be set for the first revolution of the disk 108, as set forth in step 805. More specifically, N (which represents the revolution of the disk 108 for which the ERC values are determined) is set to 1. Since no ERC was made in a prior revolution of the disk 108, the PES RRO due to ERC is set to zero for the prior revolution (N−1) of the disk 108 and the accumulated estimated runout (step 832 described below) is set to zero. Therefore, the PES RRO due to ERC for revolution 0 of the disk 108 is set to 0. In practice, the ERC values are initially set to zero in the disk drive 100.
Next, in step 810, the PES RRO for revolution N of the disk 108 is determined by track following and measuring the position error associated with each servo sector 212 in the track 132. Subsequently, in step 820, the PES RRO due to ERC for the prior revolution (N−1) of the disk 108 is added to the values determined in step 810 on a sector-by-sector basis, which results in a total PES RRO that has values associated with each servo sector 212 of the track 132 being corrected. For N=1, the PES RRO due to ERC is 0, as set forth in step 805.
In step 825, the inverse impulse response for the servo control system 144 is determined. U.S. Pat. No. 6,549,362 describes a method for determining the inverse impulse response for a servo control system by injecting or otherwise providing an impulse function into the servo control system and measuring the response of the servo control system. It should be understood that the present invention is not limited by the way the inverse impulse response of the servo control system is established.
A circular convolution of the total PES RRO (step 820) and the inverse impulse response of the servo control system 144 (step 825) is performed to obtain estimated runout values associated with each servo sector 212 (step 830), which are summed with all prior estimated runout values in an accumulator (step 832). Then, in step 835, the accumulated estimated runout values are divided by N, which results in the WRRO for revolution N of the disk 108. ERC values are determined for the track 132 based upon the WRRO for revolution N of the disk 108 and are electronically updated (step 840).
In step 845, the value of N is incremented by one in preparation for obtaining ERC values for a next revolution of the disk 108. In step 848, the impulse response of the servo control system 144 is determined. U.S. Pat. No. 6,549,362 describes a technique for obtaining the impulse response of a servo control system. Then, in step 850, the PES RRO due to the ERC values from the prior revolution (N−1) of the disk 108 is obtained by convolving the WRRO for the prior revolution (N−1) of the disk 108 with the impulse response of the servo control system 144.
After obtaining the ERC values from the prior revolution (N−1) of the disk 108 (step 840), and obtaining the PES RRO due to ERC from the prior revolution (N−1) of the disk 108 (step 850), measurements are taken of the PES RRO for revolution N of the disk 108, which now include updated ERC values (step 840) that are, preferably, applied electronically (step 810). Subsequently, in step 820, the PES RRO due to ERC for the prior revolution (N−1) of the disk 108, which was determined in step 850, is added to obtain a total PES RRO. The total PES RRO is convolved with the inverse impulse response for the servo control system 144 (step 830) to obtain an estimated runout, which is summed with the results for the prior revolutions of the disk 108 (step 832) and then divided by N to obtain the WRRO for revolution N of the disk 108 (step 835). The ERC values for the track 132 are calculated based on the WRRO for revolution N of the disk 108 and are electronically updated on a sector-by-sector basis (step 840). The process repeats until a decision is made that the total number of revolutions of the disk 108 for determining the ERC values with feedback has been met, or some other criteria has been satisfied (e.g., runout measurement, time spent on a track in question, etc.). Then, the ERC values are written to the disk drive 100 (e.g., in the servo sectors 212, in a look-up table, in memory, etc.). The feedback provided by the present invention forces errors (e.g., PES non-linearities, gain errors modeling the inverse impulse response (or plant), and errors introduced into the servo control system 144 by NRRO) to be driven to a null.
Certain other advantages may be obtained by the present invention, since it can handle gain errors associated with modeling the impulse response. For a number of reasons, including differences in skew angle, the impulse response is not the same for all tracks on a disk surface. In fact, gain variations of 5–10% may exist from the inner diameter to the outer diameter of a disk surface. Accordingly, in order to more accurately determine the WRRO for a particular track in an open-loop system, the impulse response should be measured on a track-by-track basis. However, due to the number of tracks, this becomes extremely time-consuming. Therefore, the impulse response is determined for one track of a disk surface, which presents errors in an open-loop system.
Because the closed-loop system of the present invention drives the gain errors to zero, it is more forgiving in modeling the impulse response. Accordingly, even though the impulse response is determined for one track on a disk surface, it can be used reliably with the present invention. Therefore, errors are reduced as compared to an open-loop system.
While the description in connection with
Another advantage of the present invention is that ERC values can continue to be obtained after the disk drive 100 has left the factory (e.g., is in the possession of an end user). In such case, the present invention would run in the background of normal operation for the disk drive 100.
As mentioned in the background of the invention section, due to time constraints, only the most poorly-written tracks are corrected in the manufacturing process. For even those tracks that are being corrected during the manufacturing process, only a small amount of time can be spent, which leaves room for improvement of the ERC values for the tracks.
Since the present invention can be used after manufacturing the disk drive 100, the present invention can provide the ERC values for all of the tracks 132 (which is preferred) as opposed to providing the ERC values for only some of the tracks 132. The present invention may also be used to improve the ERC values for the tracks 132. Furthermore, since the disk drive 100 parameters (e.g., flying height, head linearity, magnetic image, burst sizes, etc.) change over time, the present invention may be used to update the ERC values for all the tracks 132 (i.e., some tracks 132 can be re-done) after a period of time (e.g., a year).
In performing ERC outside of the factory, the flowchart of
Furthermore, the value of N must be set in step 805. If the prior ERC values have been calculated, N could be counted and stored in the disk drive 100 to reflect the actual number of revolutions of the disk 108 used in developing the ERC values. Instead, N may not bear any relation to the actual revolutions of the disk 108 used in developing the prior ERC values. That is, the value of N will determine how quickly the system will converge and, therefore, may be selected in accordance with design considerations. If N is too high, the system will not converge for a long period of time. However, if N is too small, the system will be very sensitive to NRRO for the first few revolutions of the disk 108 and, therefore, the RRO may temporarily increase until the NRRO can be cancelled. In one embodiment, N is 10, which is equivalent to starting the process up again after 10 revolutions of the disk 108 of error correction with feedback. It is also necessary to preload the accumulator (step 832) with values equal to N times the ERC values read from the disk drive 100.
In another embodiment of the present invention, the disk drive 100 could keep track of the tracks 132 that have been corrected by setting a flag in each servo sector 212 or by storing such information at an appropriate location on the disk surface 204 (or in the disk drive 100). In such an embodiment, a track 132 can be considered corrected if ERC updating was performed for a predetermined number of revolutions (e.g., 50 revolutions) of the disk 108. The disk drive 100 can skip tracks 132 (or servo sectors 212 in tracks 132) that have their flag set and correct tracks 132 that don't have their flag set.
In yet another embodiment, the ERC values could be obtained by moving from the outer diameter of the disk 108 to the inner diameter of the disk 108 (or visa versa). The location of the last corrected track 132 may be stored so that the process can be continued if it was interrupted.
Correcting tracks 132 in the field may pose additional problems in that, if the ERC values are changed after data has been written, it can become difficult (if not impossible) to recover the data. Therefore, in one embodiment, data from the track 132 being corrected may be stored in a buffer while the track 132 is corrected. After the ERC values are obtained for the track 132, the data is written back to the track 132, preferably while the final ERC values are written to the track 132.
The present invention may be implemented in the firmware of the controller 136 and/or the channel 140 or any other convenient place in the disk drive 100. In addition, the present invention may be implemented in a computer external to the disk drive 100.
While an effort has been made to describe some alternatives to the preferred embodiment, other alternatives will readily come to mind to those skilled in the art. Therefore, it should be understood that the invention may be embodied in other specific forms without departing from the spirit or central characteristics thereof. The present examples and embodiments, therefore, are to be considered in all respects as illustrative and not restrictive, and the invention is not intended to be limited to the details given herein.
Melrose, Thomas, Hargarten, James
Patent | Priority | Assignee | Title |
10741206, | Sep 19 2018 | Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation | Magnetic disk device and head position correction method |
11127426, | Sep 19 2018 | Kabushiki Kaisha Toshiba; Toshiba Electronic Devices & Storage Corporation | Magnetic disk device and head position correction method |
7423834, | Dec 04 2003 | Maxtor Corporation | Convolution based multiple harmonic frequency repeatable runout compensation method and apparatus |
7474491, | Dec 09 2005 | Maxtor Corporation | Adaptive write unsafe thresholds for self servo writing |
7474496, | May 06 2005 | Maxtor Corporation | Micro actuator DC gain calibration scheme for HDD dual-stage actuator systems |
7477473, | Jan 18 2006 | Maxtor Corporation | Servo positioning adjustment |
7486468, | May 10 2007 | Seagate Technology, LLC | Corrected read/write offset compensation |
7489469, | Mar 15 2006 | Seagate Technology LLC | Embedded runout correction based on written-in runout measurement |
7525754, | Jun 26 2007 | Seagate Technology LLC | Repeated runout compensation using scaled position signals |
7564642, | May 07 2007 | FUJIFILM Corporation | Apparatus, system, and method for repeatable runout cancellation using ring of integrators |
7576941, | Oct 26 2007 | Western Digital Technologies, Inc. | Disk drive writing wedge RRO values in a butterfly pattern |
7583470, | Aug 29 2007 | Western Digital Technologies, Inc. | Disk drive writing wedge RRO data along a sinusoidal path to compensate for reader/writer offset |
7589930, | Mar 14 2007 | Seagate Technology LLC | Zone based repeated runout error compensation |
7639447, | Feb 18 2008 | Western Digital Technologies, Inc. | Servo track squeeze compensation in a disk drive |
7663835, | Jun 28 2007 | Western Digital Technologies, Inc.; Western Digital Technologies, INC | System and method for identifying track squeeze errors (TSEs) of a disk of a disk drive |
7889453, | Nov 14 2007 | Seagate Technology LLC | Repeated runout error compensation using iterative feedback |
7929234, | Mar 27 2009 | Western Digital Technologies, Inc.; Western Digital Technologies, INC | Disk drive prioritizing in-the-field defect scanning based on number of write operations in each of a plurality of defect zones |
7990089, | Aug 16 2007 | MARVELL INTERNATIONAL LTD | Repetitive error correction method for disk-drive spindle motor control systems |
8004785, | May 09 2008 | Western Digital Technologies, INC | Disk drive write verifying unformatted data sectors |
8094405, | Oct 24 2007 | CAVIUM INTERNATIONAL; MARVELL ASIA PTE, LTD | Repetitive error correction method for disk-drive servo control systems |
8207696, | Feb 19 2008 | CAVIUM INTERNATIONAL; MARVELL ASIA PTE, LTD | Transfer characteristic based motor speed control |
8295004, | Dec 16 2009 | Kabushiki Kaisha Toshiba | Method and apparatus for measuring disk runout in a disk drive |
8305705, | May 05 2010 | Western Digital Technologies, Inc.; Western Digital Technologies, INC | Disk drive cross correlating track crossing signal with ideal signal to calibrate jog value |
8395341, | Aug 16 2007 | CAVIUM INTERNATIONAL; MARVELL ASIA PTE, LTD | Repetitive error correction method for disk-drive spindle motor control systems |
8565053, | Jun 19 2012 | Western Digital Technologies, Inc.; Western Digital Technologies, INC | Methods and devices for preventing media errors due to media scratches |
8643976, | Jan 31 2007 | Western Digital Technologies, Inc. | Method for improved repeatable runout learning in a disk drive |
8670206, | Mar 27 2012 | Western Digital Technologies, INC | Disk drive estimating repeatable runout of reference pattern based on repeatable runout of phase error |
8717704, | Feb 28 2012 | Western Digital Technologies, INC | Disk drive defining non-circular data tracks relative to a rotation axis of the disk |
8724253, | Mar 27 2012 | Western Digital Technologies, INC | Disk drive adjusting demodulation window for spiral track using timing feed-forward compensation |
8743495, | Jun 03 2011 | Western Digital Technologies, INC | Disk drive detecting track squeeze when circular tracks are defined from non-circular servo tracks |
8743503, | Mar 11 2013 | Western Digital Technologies, Inc.; Western Digital Technologies, INC | Disk drive updating compensation values for multiple servo sectors based on PES generated for current servo sector |
8749904, | Feb 28 2012 | Western Digital Technologies, INC | Disk drive compensating for track squeeze by writing non-circular servo tracks |
8917475, | Dec 20 2013 | Western Digital Technologies, INC | Disk drive generating a disk locked clock using radial dependent timing feed-forward compensation |
8929021, | Mar 27 2012 | Western Digital Technologies, INC | Disk drive servo writing from spiral tracks using radial dependent timing feed-forward compensation |
8934191, | Mar 27 2012 | Western Digital Technologies, Inc. | Disk drive generating a disk locked clock using radial dependent timing feed-forward compensation |
Patent | Priority | Assignee | Title |
4412165, | Oct 29 1980 | International Business Machines Corporation | Sampled servo position control system |
6115203, | Jan 30 1998 | Maxtor Corporation | Efficient drive-level estimation of written-in servo position error |
6493173, | Nov 08 1999 | Western Digital Technologies, Inc. | Headerless disk drive comprising repeatable runout (RRO) correction values recorded at a user data rate |
6545835, | Aug 31 2000 | Western Digital Corporation | Method and apparatus for RRO learning before and after shipping to cancel RRO in a disk drive |
6549362, | Jun 09 2000 | Maxtor Corporation | Method and apparatus for the enhancement of embedded runout correction in a disk drive |
6657810, | Feb 28 2001 | Western Digital Technologies, Inc.; Western Digital Corporation | Disk drive employing separate read and write repeatable runout estimated values for a head having a read element offset from a write element |
6804079, | Aug 06 2001 | Seagate Technology LLC | Written-in repeatable run-out compensation in embedded servo disc drives |
Date | Maintenance Fee Events |
Mar 12 2010 | M1551: Payment of Maintenance Fee, 4th Year, Large Entity. |
Apr 25 2014 | REM: Maintenance Fee Reminder Mailed. |
Sep 12 2014 | EXP: Patent Expired for Failure to Pay Maintenance Fees. |
Date | Maintenance Schedule |
Sep 12 2009 | 4 years fee payment window open |
Mar 12 2010 | 6 months grace period start (w surcharge) |
Sep 12 2010 | patent expiry (for year 4) |
Sep 12 2012 | 2 years to revive unintentionally abandoned end. (for year 4) |
Sep 12 2013 | 8 years fee payment window open |
Mar 12 2014 | 6 months grace period start (w surcharge) |
Sep 12 2014 | patent expiry (for year 8) |
Sep 12 2016 | 2 years to revive unintentionally abandoned end. (for year 8) |
Sep 12 2017 | 12 years fee payment window open |
Mar 12 2018 | 6 months grace period start (w surcharge) |
Sep 12 2018 | patent expiry (for year 12) |
Sep 12 2020 | 2 years to revive unintentionally abandoned end. (for year 12) |